Membrane physiology: action potential: practice question

A Physiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Physiology · Membrane physiology: action potential

Sample item

What causes the rapid depolarization phase of a neuronal action potential?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. Opening of voltage-gated sodium channels

Rapid opening of voltage-gated sodium channels allows sodium influx and drives the action potential upstroke. Subsequent sodium-channel inactivation and potassium efflux repolarize the membrane.

Option by option

  • A. Opening of potassium leak channels only

    Potassium efflux favors repolarization.

  • B. Calcium pumping out of the cell

    Calcium pumping is not the cause of the neuronal upstroke.

  • C. Closure of all ion channels

    Action potentials require selective channel opening.

  • D. Opening of voltage-gated sodium channels (correct)

    Correct. Sodium influx produces rapid depolarization.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is D, Opening of voltage-gated sodium channels. Rapid opening of voltage-gated sodium channels allows sodium influx and drives the action potential upstroke.

Why is "Opening of potassium leak channels only" not the answer?

Potassium efflux favors repolarization.

Why is "Calcium pumping out of the cell" not the answer?

Calcium pumping is not the cause of the neuronal upstroke.

Why is "Closure of all ion channels" not the answer?

Action potentials require selective channel opening.

What concept does this question test?

It tests Membrane physiology: action potential in Physiology. Subsequent sodium-channel inactivation and potassium efflux repolarize the membrane.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Membrane physiology: action potential?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.